Optical phonon features in ferroelectric Bi3Fe1/2Nb3/2O9

We have investigated the Raman scattering and infrared active optical phonons in Bi3Fe1/2Nb3/2O9. At room temperature the phonons were assigned according to lattice dynamic calculations performed using the Wilson's FG method. The infrared phonon parameters allowed us to calculate the real part of the dielectric permittivity and losses in the far infrared region, and also to estimate the quality factor (Q) of the material in the microwave region. The Raman-active phonons were investigated at high temperatures and the ferroelectric phase transition underwent by this compound was observed. The change in temperature-dependent Raman spectra suggests that the high temperature crystal structure belongs to the I4/mmm(D4h17) space group.